The present subject matter relates generally to a RDX plant indicator system. More specifically, the present invention relates to a plant indicator system designed to detect contamination of RDX using prickly sida plants as sentinels.
The continuous use of explosives on training ranges results in the development of major negative environmental impacts that are difficult to remedy. Also, the costs of environmental compliance, cleanup, pollution reduction, and conservation are significant. Existing methods to test for contamination are also dangerous since the military sites may include land mines and other explosives or explosive residues. Hexahydro-1,3,5-trinitro-1,3,5-triazine, referred to as RDX, is commonly found at military operation sites. RDX is one of the most widely distributed energetic soil contaminants. RDX is the primary energetic used in most military applications from explosives ordnance (bombs, missiles, and shells) to missile propellants and demolition charges. The United States Department of Defense (DoD) has identified more than one thousand sites with explosives contamination. Many sites became contaminated through open detonation and burning of explosives at army depots, evaluation facilities, artillery ranges, and ordnance disposal sites. Before the 1980's, waste was often dumped in unlined pits, and has now contaminated both soil and groundwater. The use of ordnance continues to pollute soil and water in the U.S. and worldwide.
As RDX readily migrates into the surface or near surface soils, it leads to soil and groundwater contamination. Soil contamination by this energetic at military ranges in the United States and Canada is well documented. Furthermore these contaminants have leached into and contaminated groundwater. Their residues are known to accumulate in soils on military ranges. Live fire training and testing ranges are placed at risk by the transport of Off Range Contaminates (ORC) through a variety of environmental pathways.
The mobility of energetic residues is a major concern. Mobility is a complex process and has many confounded effects. Among energetics, TNT and RDX are most widely distributed as soil contaminants, and both compounds are often found in the soil at the same site. RDX has a high potential for soil leaching since it does not bind to soil very strongly and can move rapidly into the groundwater. RDX is more soluble than other contaminants, but RDX is not typically absorbed or biodegraded significantly in aerobic soil. Unlike TNT, RDX does not bind to soil particles, and its breakdown products are more likely to move into the groundwater. Energetics and residues are labile in the environment and these changes can be caused through sunlight, soil microbes, and transformation by certain plant processes.
RDX does not bioaccumulate or build up in fish or people, but exposure to RDX in large amounts may cause seizures. However, the effects of long-term, low-level exposure to RDX in humans is unknown. Studies have also been made on plants and crops, and many plants have developed an uptake of RDX from contaminated soil and contaminated irrigation water. Technologies such as phytoextraction and phytostabilization has been studied in cases of TNT contamination. Phytoextraction is the use of plants to uptake, accumulate, and remove contaminants from the soil, and phytostabilization is the use of both plants and soil amendments to prevent the contaminants from moving out of the area. These methods may be used to detect contamination on military sites.
A large number of studies have been done to evaluate phytoremediation processes for energetics. However, in the studies using plants, the majority of plants are either grasses or species growing in wetland habitats. Little research has been on upland plants. Past research has focused mainly on grasses and found RDX induced inhibition of biomass production. Also, related work has been done where fluorescence was used as an indicator in monitoring uptake of explosives in genetically modified plants that were not commonly found on ranges. This approach may be more expensive, and does not provide a realistic training environment on ranges.
Also, in order to test for contamination on military sites, the safety of range personnel is often compromised in order to collect field samples and test for energetics. In areas with dense vegetation, locations of residues are more difficult to visualize and locate. Collecting these samples also disrupt military range activity and put personnel in danger since they may disrupt an unexploded land mine or other explosive. The current methods of collecting sufficient data for a comprehensive environmental assessment are also very costly.
Therefore, there is much concern regarding the migration of these contaminants, particularly RDX, to groundwater. Ecosystem components, such as vegetation cover and soil types, play important roles in determining potential pathways a contaminant may take upon leaving a particular range.
Accordingly, a need exists for a plant indicator system designed to detect contamination of RDX using naturally occurring plants such as prickly sida as sentinels as described and claimed herein.